It is believed that 50-60 million years ago, Moeritheriums, approximately the size of current day pigs, were the roots from which the proboscideans (animals with trunks) evolved. Based on both morphological and biochemical evidence, it is generally agreed that the manatees, dugongs, and hyraxes are the closest living relatives of today's elephants. All but two (the African and Asian elephants) have died out.
The trend in the evolution of Proboscidea has generally been an increase in size, related in longer limb bones and larger skulls and teeth. As Proboscideans have grown taller, their trunks have grown longer.
Because their heads are far from the ground, nature has compensated for this height by developing the trunk as a necessary tool. For such large animals, the trunk has provided a fast and convenient way of reaching food and water on the ground. This has meant that they do not have to bend down to drink or feed, which would put them in a vulnerable position. A long trunk has enabled Proboscideans to investigate the ground and eat and drink, while still watching and listening for approaching danger. As a result, nature has selected in favour of longer trunks. This is one of the elephant's most interesting and unique physical features.